Turbofan engines, commonly used to power aircraft, are a type of air-breathing jet engine that includes a fan and a core (turbine) engine that both provide propulsive flow (i.e., a portion of the thrust of the turbofan engine is generated by the fan and a portion is generated by the core engine). Generally, the propulsive flows from the fan and core engine are separately ducted through the turbofan engine and not mixed within the turbofan engine. The core engine of the turbofan engine burns fuels and therefore yields hot exhaust at high velocity even when operated at idle speeds, such as at ground idle speed.
Some operations of aircraft require that engines remain running while on the ground during onloading and/or offloading (such as in Engines Running Operations (ERO) procedures). During such operations, personnel should stay clear of hot, fast exhaust flow (sometimes called jet wash or jet blast) from aircraft engines such as turbofan engines. Conventional engines, during ground idle, may emit jet blast at a temperature of greater than 250° C. and at a speed of greater than 150 km/h.
For some ERO procedures, aircraft may employ heavy, complex core exhaust diverter mechanisms that divert hot core engine exhaust away (typically upwards) from ground personnel. A core exhaust diverter is different than a fan thrust reverser that most transport aircraft use to direct fan flow forward, e.g., to decelerate the aircraft on landing. For example, a C-17 transport aircraft may employ its core exhaust diverter and its fan thrust reversers during ERO to divert core engine exhaust and fan flow away from ground personnel and to make the environment behind the engines tolerable during ERO. Such core exhaust diverter mechanisms require extra fuel (due to weight) and extra maintenance (due to mechanical complexity).
Hence, there is a need for better mechanisms and/or methods to avoid high velocity, hot exhaust plumes emanating from the back of turbofan-powered aircraft during ground operations.